Conventionally, there has been known a power conversion circuit which includes a MOSFET having a semiconductor base substrate where a super junction structure is formed (see patent document 1, for example).
Conventionally, there has been known a MOSFET which includes a semiconductor base substrate where a super junction structure is formed of an n-type column region and a p-type column region (see patent document 1, for example).
As shown in FIG. 21, a conventional MOSFET 900 includes: a semiconductor base substrate 910 having n-type column regions 914, p-type column regions 916, a p-type base region 918 formed on surfaces of the n-type column regions 914 and surfaces of the p-type column regions 916, and an n-type source region 920 formed on a surface of the base region 918 and where a super junction structure is formed of the n-type column regions 914 and the p-type column regions 916; trenches 922 which are formed so as to reach a depth position deeper than a deepest portion of the base region 918 in regions where the n-type column region 914 is positioned as viewed in a plan view and a part of the source region 920 is exposed on an inner peripheral surface of the trench 922; and gate electrodes 926 which are embedded in the inside of the trenches 922 through gate insulation films 924 formed on inner peripheral surfaces of the trenches 922.
In this specification, “super junction structure” means a structure where an n-type column region and a p-type column region are alternately and repeatedly arranged as viewed in a predetermined cross section.
In the conventional MOSFET 900, the n-type column region 914 and the p-type column region 916 are formed such that a total amount of a dopant in the n-type column region 914 is equal to a total amount of a dopant in the p-type column region 916. That is, the n-type column region 914 and the p-type column region 916 are well-balanced with each other in terms of a charge.
The conventional MOSFET 900 includes the semiconductor base substrate 910 where the super junction structure is formed of the n-type column regions 914 and the p-type column regions 916 thus providing a switching element which has a low ON resistance and a high withstand voltage.